THE FRUIT OF WASHINGTON STATE has legendary qualities, with Vitis vinifera sharing in that reputation. Washington produces more grapes than any state other than California, and varietal wine from more than 50 wineries that often has as much complexity, and costs less, than its rivals from farther south. Half the state's production comes from riesling, a hardy grape able to withstand the winters and traditionally a favorite of the locals, but riesling is not the most interesting development today in America's northwest. Chardonnay, sauvignon blanc, semillon, gewurztraminer and cabernet sauvignon have taken on a unique character in Washington and are challenging the same wines from California and abroad.

Most of the grapes are grown in Yakima Valley and in the Columbia Valley, a recent and rather loose official appellation including an extensive and various area in the southeastern part of the state. The biggest wineries truck their grapes at night, sometimes more than 100 miles, from vineyards to crushers located closer to urban markets. "The trucks go over the pass and the fruit sets up nicelyin the cool air," says a representative of Columbia Winery, outside Seattle. Columbia is the new name for the Associated Vintners, the oldest bonded winery in the state. The grapes do seem to make the journey well enough, and Columbia is well known in the neighborhood for its riesling and gewurz, and now for a buttery chardonnay.

Also located at Seattle is the state's largest winery, Chateau Ste. Michelle, a big estate just east of the city that calls to mind the manicured grounds of Bordeaux's most famous ch.ateau. Ste. Michelle attracts many tourists and offers commercially consistent wines that are often great bargains. Noted California winemaker Andr,e Tchelistcheff has served as a consultant to Ch.ateau Ste. Michelle for years; its cabernets and merlots became the essence of "food wine" long before California came up with the marketing concept. Ste. Michelle has planted new vineyards in eastern Washington and opened a 1.5-million-gallon winery there where the reds are now made, a considerable investment in the state's varietal future.

Also in the east, at Spokane, is Arbor Crest, a 25,000-case winery with prize-winning sauvignon blanc to its credit and big plans. The six-year-old winery is about to move into a mansion on the hill built in the '20s by a chairlift magnate, which it will open up to tourists. "Sonoma and Napa counties are all planted up," says one of the owners, David Mielks, of his competition to the south. "Washington has 200,000 acres yet to be planted. Someday the court" -- the focus of the American wine industry -- "will have to move to Spokane."

That is debatable, but the list of good Washington wineries grows. It includes Quail Run Vintners (Zillah); Bookwaltes Winery (Pasco), F.W. Laugguth, a German transplant in Mattawa and Newharth Winery (Sequim). The cabernet made at Leonetti Cellar (Walla Walla), from plantings on a tiny 11/2-acre plot, was judged in one 1982 California tasting as the best cabernet made in the United States. I tasted the '82 and, although it may not be the best cab in the country, it is very good indeed.